A proton exchange membrane (PEM) fuel cell includes a cathode area, an anode area and an ion-exchange membrane that separates these areas. In operation, the anode area is supplied with, for example, hydrogen in gaseous form, and the cathode area is supplied with, for example, oxygen or ambient air containing oxygen. In the presence of a catalytic converter, the hydrogen molecules split into protons and electrons. In the cathode area, the oxygen molecules absorb electrons and are ionized into O2− ions. The protons formed in the anode area diffuse through the membrane to the cathode area and the electrons are supplied to the cathode area by way of a separate electrical conductor, with an electrical load being inserted. The protons and oxygen ions react to form water.
In order for the fuel cell to function most effectively, adequate membrane hydration is needed. The protons are transported in the membrane in the form of H3O+ ions, which is dependent upon the appropriate water content of the membrane. If the humidity is not substantially constant across the membrane, the fuel cell cannot be kept at optimum operation, as dryness makes it more difficult for proton transport.
Membrane hydration may be achieved by humidifying the fuel (e.g., the hydrogen gas) and oxidant gases (e.g., oxygen or air) prior to their introduction into the fuel cell. Generally, pre-humidification systems are complex, relatively expensive and/or require an external heat source.